Laser processing device and laser anneal device

Abstract

This laser anneal device 1 comprises: a laser irradiation unit for irradiating a semiconductor wafer 3 with a laser pulse LP for annealing; a wafer table 31 for holding the semiconductor wafer 3; and a static removal part 6 for removing static from the wafer table 31. The static removal part 6 connects the wafer table 31 to a reference potential. The wafer table 31 includes a conductive part 313 that is electrically conductive, and the static removal part 6 connects the conductive part 313 to the reference potential. The wafer table 31 includes a holding part body 311 having lower conductivity than the conductive part 313, and the conductive part 313 is provided on at least a surface of the holding part body 311.

Description

Laser processing device, laser annealing device

[0001] The present disclosure relates to a laser processing device and the like.

[0002] Patent Document 1 discloses a laser annealing apparatus that performs annealing by sequentially irradiating an irradiation area of ​​a workpiece such as a semiconductor wafer with laser pulses. The laser pulses are two-dimensionally scanned across the entire irradiation area by an appropriate laser scanning mechanism.

[0003] Japanese Patent Application Laid-Open No. 2018-67642

[0004] When a workpiece, such as a semiconductor wafer, is irradiated with a laser, contaminant particles originating from the workpiece can be generated due to ablation or evaporation of the workpiece's surface. Such contaminant particles can contaminate the inside and outside of the processing chamber in which the workpiece is placed, and can directly or indirectly interfere with the laser processing of the workpiece. In addition, the wafer chuck that holds the semiconductor wafer by suction can become electrically charged, and this static electricity can attract contaminant particles.

[0005] The present disclosure has been made in consideration of these circumstances, and aims to provide a laser processing apparatus and the like that can effectively prevent contaminant particles from being adsorbed onto a holder that holds an object to be processed.

[0006] In order to solve the above problems, a laser processing device according to one aspect of the present disclosure includes a laser irradiation unit that irradiates a laser onto a workpiece, a holding unit that holds the workpiece, and a static electricity removal unit that removes static electricity from the holding unit.

[0007] According to this aspect, static electricity is removed from the holder that holds the workpiece, so that it is possible to effectively prevent contaminant particles from being attracted to the holder.

[0008] Another aspect of the present disclosure is a laser annealing apparatus including a laser irradiation unit that irradiates a workpiece with a laser for annealing, a holder that holds the workpiece, and a static electricity removal unit that removes static electricity from the holder.

[0009] Any combination of the above components, or any conversion of these expressions into methods, devices, systems, recording media, computer programs, etc., are also encompassed within the present disclosure.

[0010] According to the present disclosure, it is possible to effectively prevent contaminant particles from being adsorbed onto the holder that holds the object to be treated.

[0011] 1A and 1B are schematic diagrams showing the configuration of a laser annealing apparatus and the peripheral configuration of a wafer table on which a semiconductor wafer is placed.

[0012] Hereinafter, with reference to the drawings, a detailed description of embodiments of the present disclosure (hereinafter also referred to as "embodiments") will be given. In the description and / or drawings, identical or equivalent components, members, processes, etc. will be designated by the same reference numerals, and redundant description will be omitted. The scale and shape of each part shown in the drawings are set for convenience to simplify the description and should not be interpreted as limiting unless otherwise specified. The embodiments are merely examples and do not limit the scope of the present disclosure in any way. Not all features and combinations thereof presented in the embodiments are necessarily essential to the present disclosure. For convenience, the embodiments are presented broken down into components for each function and / or functional group that realizes the features. However, one component in an embodiment may actually be realized by a combination of multiple separate components, or multiple components in an embodiment may actually be realized by a single integrated component. Furthermore, although multiple embodiments and variants may be disclosed in parallel, any components of each embodiment and / or each variant may be combined in any manner as long as they do not interfere with each other's functions.

[0013] 1 schematically shows the configuration of a laser annealing apparatus 1 as a laser processing apparatus according to an embodiment of the present disclosure. The laser annealing apparatus 1 is an apparatus that performs an annealing process (heating process) by irradiating a laser (e.g., laser pulses LP) emitted by a laser apparatus 2 onto a semiconductor wafer 3 (placed on a wafer table 31 fixed to a stage apparatus 4 described later) as a processing object. Note that the laser processing apparatus according to the present disclosure is not limited to the laser annealing apparatus 1, and may be any apparatus that irradiates any processing object with a laser in any manner to perform any processing, such as a laser cutter that performs laser cutting on the processing object.

[0014] The laser annealing apparatus 1 in the illustrated example is significantly simplified from the actual one, and many components that are not mentioned in the description of this embodiment (e.g., components for measuring the laser and semiconductor wafer 3, components for transporting the semiconductor wafer 3, and components for stopping laser irradiation in an emergency) are omitted.

[0015] The illustrated configuration is merely an example, and the present disclosure may be applied to laser annealing apparatuses of any other configuration. For example, in the illustrated example, the control system is composed of a laser control unit 51, a trigger pulse control unit 52, a personal computer (PC) 53, a scanner control unit 54, a stage control unit 55, etc. However, as long as the laser annealing apparatus 1 and the laser apparatus 2 can appropriately perform annealing processing on the semiconductor wafer 3, a control system of any other configuration may be provided.

[0016] In the illustrated example, an energy adjustment mechanism 11, a transmission optical system 12, a mask 13, an irradiation optical system 14, a galvanometer scanner 15, an fθ lens 16, etc. are provided along the laser path, but any other components may be provided between the laser device 2 and the semiconductor wafer 3, and these components may be arranged in any manner, as long as the laser from the laser device 2 is appropriately irradiated onto the semiconductor wafer 3. As will be described later, in the illustrated example, a combination of the laser device 2, the energy adjustment mechanism 11, the transmission optical system 12, the mask 13, the irradiation optical system 14, the galvanometer scanner 15, the fθ lens 16, etc. constitutes a laser irradiation unit that irradiates the semiconductor wafer 3, which is the workpiece, with a laser pulse LP as a laser.

[0017] In the following, directions related to the configuration and / or operation of the laser annealing apparatus 1 will be described based on a three-dimensional Cartesian coordinate system in which the mutually orthogonal X, Y, and Z axes are the coordinate axes. For convenience, the X and Y directions are assumed to be horizontal (i.e., the XY plane is the horizontal plane), and the Z direction is assumed to be vertical. As will be described later, the semiconductor wafer 3 is driven within the XY plane relative to the laser from the laser apparatus 2 under the control of the scanner control unit 54 and / or the stage control unit 55.

[0018] For example, the semiconductor wafer 3 is driven in the X direction together with the moving table 41 of the stage device 4, which is driven in the X direction by the stage control unit 55 (the X direction in this case is also referred to as the driving direction), and the laser from the laser device 2 is scanned in the Y direction by the galvanometer scanner 15, which is controlled by the scanner control unit 54 (the Y direction in this case is also referred to as the scanning direction). The semiconductor wafer 3 is also driven in the Z direction together with the lift table 42 of the stage device 4, which is driven in the Z direction by the stage control unit 55 (the Z direction in this case is also referred to as the lift direction). This Z direction is also the incident direction of the laser beam incident on the semiconductor wafer 3. Hereinafter, for convenience, the X direction will also be referred to as the vertical direction, the Y direction will also be referred to as the horizontal direction, and the Z direction will also be referred to as the height direction.

[0019] The laser device 2 is a pulse laser device that oscillates laser pulses LP at a frequency of, for example, 100 kHz or higher under the control of a laser control unit 51. To fully obtain the functions and effects of the laser annealing apparatus 1 according to this embodiment, the frequency of the laser pulses LP oscillated by the laser device 2 is, for example, between 100 kHz and 10 MHz, preferably between 500 kHz and 5 MHz, and more preferably between 700 kHz and 3 MHz. In this embodiment, unless otherwise specified, the frequency of the laser pulses LP oscillated by the laser device 2 is assumed to be 1 MHz. The laser device 2 according to this embodiment may be configured, for example, as a fiber laser device that oscillates laser pulses LP using an optical fiber.

[0020] A laser pulse LP is emitted, for example, in the X direction from a laser device 2. A laser annealing device 1 that guides this laser pulse LP to a semiconductor wafer 3 that is an irradiation target (workpiece) is provided with an energy adjustment mechanism 11, a transmission optical system 12, a mask 13, an irradiation optical system 14, a galvanometer scanner 15, and an fθ lens 16, in this order, along the path of the laser pulse LP (schematically shown by a dashed dotted line).

[0021] The energy adjusting mechanism 11 adjusts the energy and energy density of the laser pulse LP emitted from the laser device 2 to values ​​suitable for the desired annealing process.

[0022] The transmission optical system 12 is an optical system that transmits the laser pulse LP. The transmission optical system 12 is composed of any optical elements such as lenses, mirrors, prisms, filters, and diffraction gratings, and may be responsible not only for transmitting the laser pulse LP but also for adjusting the size (diameter) of the laser pulse LP, shaping the laser pulse LP, and adjusting the intensity distribution of the laser pulse LP. The adjustment of the size (diameter) of the laser pulse LP and the shaping of the laser pulse LP may be performed using a mask 13 having a size (diameter) and / or shape suitable for the intended annealing process. The irradiation optical system 14 is composed of any optical elements such as lenses, mirrors, prisms, filters, and diffraction gratings, and adjusts the laser pulse LP to a form (e.g., size (diameter), shape, intensity distribution) suitable for irradiating the semiconductor wafer 3.

[0023] The galvanometer scanner 15 is a laser scanning unit that scans the laser pulse LP adjusted by the irradiation optical system 14 and the like along the Y direction. The galvanometer scanner 15 includes a galvanometer mirror 151 as a drivable optical element that reflects the incident laser pulse LP and directs it toward a desired scanning position in the Y direction, and a motor (not shown) that drives the galvanometer mirror 151 to a desired attitude or angle. The attitude or angle of the galvanometer mirror 151 is adjusted by the motor, so that the laser pulse LP incident on the galvanometer mirror 151 is reflected toward a desired position in the Y direction.

[0024] The laser scanning unit that directs the incident laser pulse LP to a desired scanning position in the Y direction is not limited to the galvanometer scanner 15, but may be configured with optical elements such as a polygon mirror scanner having a rotatable polygon mirror (optical element) or a drivable MEMS (Micro Electro Mechanical Systems) mirror. Furthermore, the scanning direction of the laser pulse LP by the laser scanning unit such as the galvanometer scanner 15 is not limited to the Y direction, but may be a direction intersecting the Y direction, such as the X direction, or may be two directions, the X direction and the Y direction. As in the latter case, when the laser scanning unit such as the galvanometer scanner 15 can scan the laser pulse LP across the XY plane, i.e., the surface of the semiconductor wafer 3, a stage device 4 (moving table 41) that drives the semiconductor wafer 3 and wafer table 31 in the X direction, etc., may not be provided. In this case, the galvanometer scanner 15 or the like constitutes a laser scanning unit in two directions, the X direction and the Y direction.

[0025] The fθ lens 16 focuses the laser pulse LP scanned in the Y direction by the galvanometer scanner 15 onto the semiconductor wafer 3 to be annealed. The laser pulse LP from the fθ lens 16 is incident on the semiconductor wafer 3 in the Z direction. The laser pulse LP focused on the semiconductor wafer 3 by the fθ lens 16 in this manner moves in the Y direction on the surface of the semiconductor wafer 3 as a result of scanning in the Y direction by the galvanometer scanner 15. The size of the laser pulse LP focused on the semiconductor wafer 3 can be designed as desired, but is preferably between 0.10 mm square and 0.15 mm square, for example, and more preferably between 0.12 mm square and 0.13 mm square. Furthermore, the scanning speed of the laser pulse LP in the Y direction on the surface of the semiconductor wafer 3 (and / or the driving speed of the semiconductor wafer 3 in the X direction by the stage device 4 (moving table 41)) can also be designed arbitrarily, but is preferably between 100 cm / s and 500 cm / s, for example, and more preferably between 250 cm / s and 350 cm / s.

[0026] The moving table 41 in the stage device 4 is a driving device that drives the semiconductor wafer 3 and the wafer table 31 relative to the laser pulse LP in the X direction. The moving table 41 moves the laser pulse LP relative to the surface of the semiconductor wafer 3 in the X direction.

[0027] As described above, by combining scanning of the laser pulse LP in the Y direction by the galvanometer scanner 15 as a Y-direction laser scanning unit and driving of the semiconductor wafer 3 in the X direction by the moving table 41 as an X-direction laser scanning unit, the laser pulse LP can be scanned across the XY plane, i.e., the surface of the semiconductor wafer 3. Note that the driving direction of the semiconductor wafer 3 by the moving table 41 is not limited to the X direction, but may be a direction intersecting the X direction, such as the Y direction, or may be two directions, the X direction and the Y direction. As in the latter case, when the moving table 41 can drive the semiconductor wafer 3 relative to the laser pulse LP across the XY plane, the galvanometer scanner 15 that scans the laser pulse LP in the Y direction, etc., may not be provided. In this case, the moving table 41 forms a laser scanning unit in two directions, the X direction and the Y direction.

[0028] The laser annealing apparatus 1 and the laser apparatus 2 as described above are controlled by a control system including a laser control unit 51 , a trigger pulse control unit 52 , a personal computer 53 , a scanner control unit 54 , and a stage control unit 55 .

[0029] The laser control unit 51 controls the laser pulses LP oscillated by the laser device 2 based on various control parameters. Examples of the control parameters include the energy of the laser pulses LP, the energy density of the laser pulses LP, the repetition frequency of the laser pulses LP, the duration (pulse width) of the laser pulses LP, the peak intensity of the laser pulses LP, the profile (e.g., intensity distribution) of the laser pulses LP, the delay time (time difference) when a plurality of laser devices 2 (not shown) irradiate the same location with laser pulses LP, and the overlap rate (the rate at which irradiation marks overlap) between adjacent rows (or adjacent columns) when the laser pulses LP are scanned back and forth.

[0030] The trigger pulse control unit 52 generates a trigger pulse synchronized with the laser pulse LP oscillated by the laser device 2, based on the synchronization signal provided from the laser control unit 51. For example, the frequency of the trigger pulse generated by the trigger pulse control unit 52 is 1 / N (N is any natural number) or N times the repetition frequency or oscillation frequency of the laser pulse LP.

[0031] The scanner control unit 54 controls the galvanometer scanner 15 (scanner control) based on the trigger pulse processed as needed by the personal computer 53. Similarly, the stage control unit 55 controls the moving table 41 (stage control) of the stage device 4 based on the trigger pulse processed as needed by the personal computer 53. In this way, based on the trigger pulse synchronized with the laser pulse LP, the scanner control unit 54 can appropriately cause the galvanometer scanner 15 to scan the laser pulse LP in the Y direction, and the stage control unit 55 can appropriately cause the moving table 41 to drive the semiconductor wafer 3 in the X direction.

[0032] FIG. 2 schematically illustrates the configuration of the vicinity of a wafer table 31 on which a semiconductor wafer 3 is placed. The wafer table 31 is a holder that holds a semiconductor wafer 3 as a processing object. The wafer table 31, also called a wafer chuck, includes a flat holder main body 311 (also called a chuck plate) on whose surface (top surface in FIG. 2 ) the semiconductor wafer 3 is placed, and a number of suction holes 312 periodically provided on the surface of the holder main body 311. The interior of each suction hole 312 is depressurized to, for example, a vacuum state by a vacuum pump 8 or the like, and the semiconductor wafer 3 is sucked into each suction hole 312 and held or fixed by the pressure difference between the chamber or processing chamber 7 in which the semiconductor wafer 3 and the wafer table 31 are placed. Each suction hole 312 preferably extends in the height direction (vertical direction in FIG. 2 ) at least on the side facing the semiconductor wafer 3 (upper side in FIG. 2 ).

[0033] In the illustrated example, the holder body 311 is made of a material with relatively low conductivity or an insulating material. For example, the holder body 311 is made of aluminum oxide or alumina. Even if the holder body 311 has low conductivity, the holder body 311 can become charged through the laser pulse LP, the semiconductor wafer 3, the atmosphere in the processing chamber 7, and the like. The charged holder body 311 may attract contaminant particles in the processing chamber 7 due to the static electricity.

[0034] Contamination particles in the processing chamber 7 include, for example, particles generated by ablation or evaporation when the semiconductor wafer 3 is irradiated with the laser pulse LP. These contaminant particles may include particles of the material of the semiconductor wafer 3 itself (e.g., silicon), as well as particles of metals, insulators, semiconductors, and the like derived from layers formed on the semiconductor wafer 3 during the semiconductor process. These contaminant particles may contaminate the inside and outside of the processing chamber 7 in which the semiconductor wafer 3 is placed, and may directly or indirectly interfere with the processing of the semiconductor wafer 3 by the laser pulse LP. Furthermore, these contaminant particles may themselves be electrically charged, and their accumulation on the holder main body 311 may further charge the holder main body 311.

[0035] Contaminant particles in the processing chamber 7 may be attracted to and accumulate between the back surface of the semiconductor wafer 3 (the lower surface in FIG. 2 ) and the surface of the holder body 311. In particular, as in the illustrated example, if the outer peripheral edge of the semiconductor wafer 3 (the left end and / or the right end in FIG. 2 ) protrudes outward from the outer periphery of the outermost suction holes 312, contaminant particles may accumulate in a concentrated manner in the gap between the lower surface of the semiconductor wafer 3 facing the outer peripheral edge and the surface of the holder body 311.

[0036] Therefore, in this embodiment, a static electricity removal unit 6 is provided to remove static electricity from the wafer table 31, which may become charged as described above. In the illustrated example, the static electricity removal unit 6 connects the wafer table 31 to a predetermined reference potential such as earth potential or ground potential. The wafer table 31 and / or the holder main body 311, which are maintained at the reference potential in this manner, prevent charging by dissipating static electricity applied from the outside to the reference potential point. According to this embodiment, static electricity is removed from the wafer table 31 that holds the semiconductor wafer 3, so that it is possible to effectively prevent contaminant particles from being attracted to the wafer table 31.

[0037] Furthermore, according to this embodiment, static electricity can be removed from the surface of the wafer table 31 with which the back surface of the semiconductor wafer 3 comes into contact, so that semiconductor elements and semiconductor circuits that may be formed on the back surface can be protected from static electricity, and electrostatic discharge (ESD) and electrostatic breakdown can be effectively prevented.

[0038] As described above, if the conductivity of holder body 311 made of alumina or the like is low, it is possible that static electricity remover 6 will not be able to properly maintain holder body 311 at the reference potential. Therefore, it is preferable to provide conductive portion 313 on at least the surface of wafer table 31 and / or holder body 311. Conductive portion 313 is made of carbon, metal, or the like, which has higher conductivity than holder body 311. In other words, holder body 311 has lower conductivity than conductive portion 313.

[0039] In this case, static electricity remover 6 connects conductive portion 313 to the reference potential. As in the illustrated example, when static electricity remover 6 is provided on the back surface of wafer table 31 and / or holder main body 311, conductive portion 313 is formed across wafer table 31 and / or holder main body 311 so as to provide electrical continuity between the front and back surfaces of wafer table 31 and / or holder main body 311. Conductive portion 313, which is maintained at the reference potential in this manner, effectively prevents charging of at least the front surface of wafer table 31 (preferably the entire surface including the side surfaces and back surface).

[0040] As shown in the example, the conductive portion 313 may be formed of a conductive film or conductive coating that covers at least a portion (preferably the entirety) of the surface of the holder body 311. Alternatively, when the holder body 311 is formed of a porous ceramic such as a sintered body of alumina, the conductive portion 313 may be formed of conductive particles that have entered the pores of the porous holder body 311. Such a conductive portion 313 may be formed by dusting the porous holder body 311 with conductive particles such as carbon powder or metal powder and then performing an appropriate fixing process.

[0041] In the above example, holder main body 311 is made of a material such as alumina, which has low conductivity, but holder main body 311 and / or substantially the entire wafer table 31 may be made of a material such as metal, which has high conductivity. In this case, there is no need to additionally provide conductive portion 313 to conductive holder main body 311.

[0042] The present disclosure has been described above based on the embodiments. Various modifications are possible to the combinations of the components and processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present disclosure.

[0043] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROM, RAM, and various integrated circuits. Examples of software resources include operating systems, applications, and other programs.

[0044] The present disclosure relates to a laser processing device and the like.

[0045] REFERENCE SIGNS LIST 1 laser annealing device, 2 laser device, 3 semiconductor wafer, 4 stage device, 6 static electricity removal unit, 7 processing chamber, 15 galvanometer scanner, 31 wafer table, 41 moving table, 311 holder main body, 312 suction hole, 313 conductive part, LP laser pulse.

Claims

1. A laser processing apparatus comprising: a laser irradiation unit that irradiates a workpiece with a laser; a holding unit that holds the workpiece; and a static electricity removal unit that removes static electricity from the holding unit.

2. The laser processing apparatus according to claim 1, wherein the static electricity removing unit connects the holding unit to a reference potential.

3. The laser processing apparatus according to claim 2, wherein the holding section includes a conductive section that is conductive, and the static electricity removing section connects the conductive section to the reference potential.

4. The laser processing device according to claim 3, wherein the holding portion includes a holding portion main body having a lower conductivity than the conductive portion, and the conductive portion is provided on at least a surface of the holding portion main body.

5. The laser processing device according to claim 4, wherein the conductive portion is constituted by a conductive film covering at least a portion of the surface of the holding portion main body.

6. The laser processing apparatus according to claim 4, wherein the conductive portion is constituted by conductive particles contained in pores in the porous holder body.

7. A laser annealing apparatus comprising: a laser irradiation unit that irradiates a workpiece with a laser for annealing processing; a holding unit that holds the workpiece; and a static electricity removal unit that removes static electricity from the holding unit.

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